1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and a method for manufacturing the same. More particularly, the present invention relates to a liquid crystal display device that employs a white sub-pixel among RGBW-4 sub-pixels as a view control component to realize a narrow viewing angle as well as a wide viewing angle in a fringe field switching mode, and a method for manufacturing the same.
2. Discussion of the Related Art
In recent years, rapid advances in the performance of an active matrix liquid crystal display (“LCD”) device have resulted in various applications of the LCD device, such as screens for flat panel TVs, and monitors for portable computers.
Among the active matrix LCD devices, a twisted nematic (TN) type LCD device is widely used. The TN type LCD device refers to an LCD device wherein, with liquid crystals arranged to have liquid crystal director twisted 90 degrees between two substrates, each having an electrode, the liquid crystal director is driven via application of a voltage to the electrodes.
Although the TN type LCD device has been spotlighted in terms of its excellent contrast and color reproducibility, it suffers from a significant problem in that it has a narrow viewing angle.
In order to solve the problem of the TN type LCD device having the narrow viewing angle, a fringe field switching (“FFS”) mode type LCD device has been introduced, wherein a counter electrode and a pixel electrode are formed of a transparent conductor, and are spaced apart by a narrow distance to allow liquid crystal molecules to be operated by a fringe field created between the counter electrode and the pixel electrode.
The FFS mode type LCD device will be described in detail hereinafter.
FIG. 1 is a plan view illustrating a related art FFS mode type liquid crystal display device, and FIG. 2 is a cross-sectional view taken along line I-I′ of FIG. 1.
In FIGS. 1 and 2, the related art FFS mode type LCD device comprises a TFT array substrate 11, which is formed thereon with gate lines 12 and data lines 15, formed of metal, crossing each other to define sub-pixels, a common line 25 disposed in parallel to the gate line 12, a thin film transistor formed at each crossing portion of the gate and data lines to act as a switching element to switch a voltage on/off, and a counter electrode 24 and a pixel electrode 17 formed of a transparent metal in each sub-pixel while being isolated from each other via a dielectric layer so as to overlap with each other; Here, the counter electrode 24 is brought into contact with the common line 25.
More specifically, the counter electrode 24 is formed in a plate shape within each sub-pixel, and the pixel electrode 17 is divided into plural sub-pixel electrodes in a direction of the data lines to define slits 60 between the sub-pixel electrodes. Here, when a Vcom signal is applied to the counter electrode 24, and a pixel signal is applied to the pixel electrode 17 through the thin film transistor, a fringe field is generated between the counter electrode 24 and the pixel electrode 17.
Each of the slits 60 has a width of about 2-6 gm, and liquid crystals are driven by the fringe field generated between the counter electrode 24 and the pixel electrode 17. In other words, when voltage is not applied, the liquid crystals are rotated from an initial orientation by the fringe field E via rubbing, and allow light to be transmitted therethrough.
Meanwhile, a color filter array substrate 21 is assembled opposite the TFT array substrate 11 with a liquid crystal layer 31 interposed therebetween, in which the color filter array substrate 21 comprises RGB-color filter layers 23 arranged in a predetermined pattern to realize red, green and blue colors, and black matrices 22 to partition the RGB-color filter layers from each other while shielding light.
The color filter layers 23 are formed such that respective sub-pixels have their own single pigment and are independently driven to exhibit color of one pixel via combination thereof.
The RGB-color filter layers 23 in the LCD device can be arranged in a stripe type, a mosaic type, a delta type, a quad type, and the like according to an arranging manner of the layers, and can be arranged in various arrays according to the size of a liquid crystal display panel, shape of the color filter, and color arrangement.
Such a related art liquid crystal display device has problems as follows.
For the related art FFS mode type LCD device, it is necessary to enable easy conversion between a narrow viewing angle and a wide viewing angle in order to prevent private information of an user from being seen by other persons near the user. To this end, a view control layer can be additionally formed in the device, or a view control electrode can be additionally formed on the overall upper plate to control the viewing angle. However, these techniques have some problems as follows. First, the view control effect is insignificant. Secondly, enlargement in the range of the electrode structure modified or added to increase the view control effect is very disadvantageous in view of an aperture ratio. Thirdly, a front contrast ratio (CR) can also be significantly reduced upon the narrow viewing angle.
The most important problem of these techniques is in a complicated driving method due to insertion of the additional electrode layer and application of signals.